Device for controlling the delivery of a combustible gas to a burner apparatus

ABSTRACT

A device for controlling the delivery of a combustible gas to a burner apparatus is provided including a main gas-delivery duct in which there is at least one servo-assisted diaphragm valve including a valve seat associated with a corresponding closure member with diaphragm control for opening the seat against the action of a resilient biasing member. The diaphragm valve includes a respective control solenoid valve with an electromagnetic operator for controlling the corresponding valve, the solenoid valve being arranged to bring about the opening/closure of a duct of a respective servo-assisted control circuit so as to operate the closure member of the valve indirectly, by the diaphragm control. The duct of the control circuit putting a portion of the main duct that is disposed upstream of the valve seat with respect to the direction of the gas-flow into flow communication with a respective control chamber of the diaphragm valve.

TECHNICAL FIELD

The present invention relates to a device for controlling the deliveryof a combustible gas to a burner apparatus according to thecharacteristics set out in the preamble to main Claim 1.

BACKGROUND ART

The invention relates particularly but not exclusively to the field ofdevices for the multifunctional control of the delivery of combustiblegases to burners of heating apparatus in general, in which the flame isintended for the direct heating of the environment or of an intermediatefluid circulating in a boiler system.

A typical known solution provides for a pair of servo-assisted valvesthat are arranged in series along the gas line, wherein the main safetyvalve (of the on-off type) is also a servo-valve with an electromagneticoperator for controlling its servo circuit. A device having theabove-mentioned characteristics is known, for example, from theApplicant's International application PCT/IT2005/000686.

In this solution, in a condition of equilibrium of the pressure andresilient forces involved, the resilient force acting on the closuremember of the main servo-valve is affected by the forces which areinduced by the delivery pressure and which act in a direction such as tounload the biasing spring. In order to reduce pressure losses, thisinvolves the use of biasing springs with resilient forces of lowmagnitude; however, in the event of obstruction of the travel of theclosure member or accidental jamming thereof, these springs would noteffectively be able to provide the resilient force necessary to closethe closure member and would not guarantee the shutting-off of thepassageway for the gas through the valve seat, thus compromising safetyin the closure of the valve seat in malfunction conditions.

It would therefore be desirable to be able to use biasing springs which,in an equilibrium condition, can exert resilient forces much greaterthan those normally to be found in known devices.

DESCRIPTION OF THE INVENTION

The problem underlying the present invention is that of providing adevice for controlling the delivery of a combustible gas to a burnerapparatus which is designed structurally and functionally to overcomethe limitations discussed with reference to the prior art mentioned.

This problem is solved by the invention by means of a device forcontrolling the delivery of a combustible gas to a burner apparatusformed in accordance with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomeclearer from the following detailed description of some preferredembodiments thereof which are described by way of non-limiting example,with reference to the appended drawings, in which:

FIG. 1 is a longitudinal section through a device formed in accordancewith the present invention,

FIG. 2 is a longitudinal section through a multifunctional valve unitcomprising the device according to the invention, and

FIG. 3 is a longitudinal section through a variant of the valve unit ofFIG. 2.

PREFERRED EMBODIMENTS OF THE INVENTION

With initial reference to FIG. 1, a device formed in accordance with thepresent invention for controlling the delivery of a combustible gas to aburner apparatus is generally indicated 1.

The device 1 comprises a main gas-delivery duct 2 extending between agas input section 3 and a gas output section 4 where the gas is suppliedtowards a main burner, not shown in the drawing.

A servo-assisted diaphragm valve, generally indicated 5 and disposed inthe main duct 2, comprises a valve seat 5 a associated with acorresponding closure member 5 b with diaphragm control 6 for openingthe seat 5 a against the action of a resilient biasing means such as aspring 7.

The diaphragm valve 5 performs the function of a main on-off valve forthe safety closure of the main gas line and is associated with a controlsolenoid valve of the servo-control circuit which control solenoid valveis indicated 8 and is arranged for opening/closing a control duct 9 ofthe servo circuit which constitutes the duct for tapping off thepressure signal for transfer to a control chamber 10 of theservo-assisted circuit, as will be explained in detail in the followingdescription. The diaphragm 6 acts directly on a control rod 11 of theclosure member 5 b which in turn is urged into closure of the seat bythe spring 7.

A first side 6 a of the diaphragm 6 defines the control chamber 10 whichis in communication with the main duct 2 upstream of the servo-valve 5by means of the control duct 9. In greater detail, the duct 9 defines afirst portion 9 a which communicates with the input section and in whichthe solenoid valve 8 is disposed, and a second portion 9 b which formsan extension of the first portion and is in communication with thechamber 10. In the region of the solenoid valve 8, the respectiveportion of the duct 9 is opened or closed selectively by means of anelectromagnet 12 of the on-off type with resilient biasing which acts ona closure element 13 that is associated with the passageway through theduct 9 and is movable away from and towards a position in which thepassageway is shut off.

The duct 9 performs the function of a duct for tapping off the pressuresignal for transfer to the control chamber 10 of the servo-assistedcircuit.

An auxiliary pilot duct, indicated 14, branches off the duct 9 in aportion thereof that is downstream of the solenoid valve 8; theauxiliary duct is arranged for the supply of a pilot burner with achoking nozzle 15.

A member, generally indicated 20, for regulating the pressure of the gasdelivered, is disposed in the main duct 2 downstream of the valve 5 andis shown only schematically in FIG. 1. This member may comprise, forexample, a pressure modulator with a motor-driven actuator, or maycomprise a second servo-valve arranged in series with the valve 5 andoperatively connected to a diaphragm pressure regulator, this secondconstructional solution being shown in FIG. 2 and described in greaterdetail below.

With further reference to the valve 5, a second side of the diaphragm,indicated 6 b and opposite to the side 6 a, defines a space 21 which isseparated from the portion of the duct 2 that extends downstream of thevalve seat 5 a so that the second side 6 b of the diaphragm is notsubjected to the delivery pressure of the gas that is present in theportion of the duct 2 downstream of the valve seat 5 a.

In greater detail, the space 21 defines a chamber that is delimitedjointly by the side 6 b and by a facing wall 22, the chamber being opento the exterior through a hole 23 so that the second side 6 b of thediaphragm is subjected to atmospheric pressure.

The control rod 11 of the closure member extends through the wall 22 andhas an end 11 a fixed firmly to the closure member 5 b and a second,opposite end 11 b which can contact the diaphragm 6 for the operativemovement of the closure member away from and towards the valve seat.

A second, flexible diaphragm 24 is preferably mounted in the wall 22 andfixed firmly to the rod 11; by virtue of its flexibility, the diaphragm24 permits axial movement of the rod during the operative travel for theopening/closure of the valve seat.

The second diaphragm 24 and the closure member 5 b advantageously haverespective mutually facing sides which have surface extensions that aresubstantially equivalent to one another so as to render the resultant ofthe stresses generated in the device by the delivery pressure acting onthe above-mentioned sides of the closure member and of the seconddiaphragm generally such as to have no effect or even to be zero.

By virtue of the provision of the chamber 21 interposed between the duct2 and the control chamber 10, the gas delivery pressure does not act onthe side 6 b of the diaphragm 6 which, on the contrary is subjected toatmospheric pressure. As a result, in equilibrium conditions, theresilient force of the spring 7 is not affected by the delivery pressure(tending to unload the spring) and, moreover, is substantially equal tothe force induced by the supply pressure acting on an area equivalent tothe difference between the area of the diaphragm 6 and the area of theclosure member 5 b.

For given conditions, it is thus possible to use a biasing spring whichexerts a resilient force that can be considerably greater (even fivetimes) than the resilient forces of the springs used in known solutions.The opening/closure of the closure member can thus be controlled morereliably and safely, facilitating the urging of the valve seat into theclosure position when the gas passageway is to be shut off.

FIG. 2 shows schematically one of the possible applications of thedevice according to the invention in a valve unit for modulating gasdelivery pressure in which details similar to those of the embodiment ofFIG. 1 are indicated by the same reference numerals.

In this application, the diaphragm valve 5 having the function of themain on-off valve is combined with the regulator member 20 whichcomprises a second servo-valve 25 arranged in series with the firstvalve 5 and in turn including a diaphragm pressure regulator 30.

The diaphragm servo-valve 25 is disposed downstream of the valve 5 withrespect to the direction of flow of the gas delivered through the duct 2and comprises a respective servo-assisted circuit including a respectivevalve seat 25 a associated with a corresponding closure member 25 b withdiaphragm control 25 c for opening the seat 25 a against the action of aresilient biasing means such as a spring 27.

The second portion 9 b of the duct 9 is in communication with a controlduct 28 in which there is a solenoid valve 29 arranged for theservo-assistance control of the servo-valve 25 as provided for the valve5.

The second solenoid valve 29 is structurally and functionally equivalentto the solenoid valve 8.

In the region of the solenoid valve 29, the respective portion of duct28 is opened or closed selectively by means of an electromagnet 29 a ofthe on-off type with resilient biasing, acting on a closure element 31associated with the passageway through the duct 28 and movable away fromand towards a position in which it shuts off that passageway.

The duct 28, together with the portion of the duct 9 communicatingtherewith, performs the function of a duct for tapping off the pressuresignal for transfer to a control chamber 32 of the respectiveservo-assisted circuit, the chamber 32 being defined on one side by thediaphragm 25 c.

A constriction, indicated 26 a, is provided in the duct 28 and, inparticular, in the portion thereof which is disposed between thesolenoid valve 29 and the control chamber 32.

In this embodiment, the pilot duct 14 branches from a portion of theduct 9 that is disposed between the solenoid valves 8 and 29 (upstreamof 29 and downstream of 8).

The control chamber 32 is also connected to the output section 4 of themain duct 2, downstream of the valve seat 25 a of the second servo-valve25, by means of a respective discharge duct 33 in which a constriction34 is advantageously provided.

The control duct 28 also branches, in a portion upstream of the controlchamber 32, into a duct 35 which is connected to the discharge, that is,which is in communication with the output section 4 of the main duct 2,downstream of the valve seat 25 a. The pressure regulator 30, which isshown schematically in FIG. 2, is advantageously provided in the duct35. The pressure regulator is a conventional diaphragm pressureregulator, in which one side of the diaphragm defines a control chamber36 communicating with the output section 4 of the duct 2 by means of aportion 35 a of the duct 35, and can also shut off the output section ofthe other portion 35 b of the duct 35 which communicates with thechamber 32. The opposite side of the diaphragm is acted on by acalibration spring 37 disposed in a chamber which is open to theatmosphere through a hole 38. The pressure regulator 30 is designed toreact to and compensate for variations in delivery pressure and to bringthe pressure back to a calibration value preset by adjustment of thespring 37.

In operation, with the electromagnets 12, 29 a de-energized, the tappingducts 9, 28 communicating with the control chamber are shut off (by therespective solenoid valves 8, 29) and the resilient biasing force of thesprings 7, 27 ensures the closure of both valve seats 5 a, 25 a of therespective servo-valves. Upon a demand for the burner to be lit, firstof all solely the electromagnet 12 is energized and, by opening the duct9, allows gas to be supplied to the pilot burner and arranges for theopening of the diaphragm valve 5 under the control of the pressurecollected in the control chamber 10 by means of the tapping duct 9 (inthe portions 9 a and 9 b). During this pilot-burner lighting stage, thetapping duct 28 communicating with the control chamber 32 is still shutoff by the solenoid valve 29 (with its electromagnet 29 a de-energized)ensuring the closure of the valve seat 25 a.

After the pilot burner has been correctly lit, the second electromagnet29 a is also energized and the tapping duct 28 is consequently openedfor the flow of gas and a corresponding pressure, correlated with theinput pressure, is produced in the control chamber 32. The diaphragm 25c, which is acted on by the force of the above-mentioned pressure thustends to lift the respective closure member 25 b from the correspondingseat 25 a, allowing gas to flow through the main duct 2 towards the mainburner. The delivery pressure is also regulated by the diaphragmpressure regulator 30.

It should be understood that the regulator member 20 described aboverepresents only one of the possible embodiments of the pressuremodulator that can be combined with the main valve 5, other types beingequally applicable and sharing the same inventive concept relating tothe main valve 5 described above.

FIG. 3 shows a variant of the valve unit of FIG. 2 in which detailssimilar to those of the previous embodiment are indicated by the samereference numerals.

This variant differs from that of FIG. 2 mainly in that the duct 28 fortapping off the control pressure for the servo-valve 25 extends betweenthe control chamber 32 and a portion of the main duct 2 disposed betweenthe valve seats 5 a and 25 a. The solenoid valve 29 for theservo-assistance operation of the servo-valve 25 is provided in thisduct 28. In this embodiment, the (pressure) signal for operating thediaphragm servo-valve 25 is tapped off in a position of the duct 2 thatis disposed between the valves 5 and 25, in contrast with the previousembodiment (FIG. 2) in which the signal tap was in series with thesolenoid valve 8.

The advantage of this embodiment (FIG. 3) is that the opening of thediaphragm servo-valve 25 is dependent on the diaphragm valve 5 beingopen.

The invention thus achieves the objects proposed, affording theadvantages mentioned over known solutions.

1. A device for controlling the delivery of a combustible gas to aburner apparatus, comprising a main gas-delivery duct (2) in which thereis at least one servo-assisted diaphragm valve (5) including a valveseat (5 a) associated with a corresponding closure member (5 b) withdiaphragm control (6) for opening the seat against the action of aresilient biasing member (7), the diaphragm valve (5) comprising arespective control solenoid valve (8) with an electromagnetic operatorfor controlling the opening/closure of the corresponding valve (5), thesolenoid valve being arranged to bring about the opening/closure of aduct (9) of a respective servo-assisted control circuit so as to operatethe closure member (5 b) of the valve (5) indirectly, by the diaphragmcontrol, the duct of the control circuit putting a portion of the mainduct (2) that is disposed upstream of the valve seat (5 a) with respectto a direction of the gas-flow into flow communication with a respectivecontrol chamber (10) of the diaphragm valve, a first side (6 a) of thediaphragm (6) of the diaphragm control being subjected to the pressureexisting in the respective control chamber (10), the second, oppositeside (6 b) of the diaphragm (6) delimits a space (21) which is separatedfrom the portion of the main duct (2) that extends downstream of thevalve seat so that the second side (6 b) of the diaphragm is notsubjected to the delivery pressure of the gas that is present in theduct portion, downstream of the valve seat (5 a); wherein a seconddiaphragm (24) and the closure member (5 b) have respective facing sideswhich have respective surface extensions that are substantiallyequivalent to one another so as to render the resultant of stressesgenerated in the device by the pressures acting on the facing sides ofthe closure member and of the second diaphragm generally such as to haveno effect or even to be zero.
 2. A device according to claim 1, whereinthe space delimited by the second, opposite side (6 b) of the diaphragmdefines a second chamber (21) which is open to the exterior so that thesecond side (6 b) of the diaphragm is subjected to atmospheric pressure.3. A device according to claim 2, wherein the second chamber (21)comprises, on a side remote from the diaphragm (6), a wall (22) throughwhich a rod (11) extends for the control of the closure member (5 b),the rod (11) having a first end fixed firmly to the closure member and asecond, opposite end that can contact the control diaphragm (6).
 4. Adevice according to claim 3, wherein the second, flexible diaphragm(24), fixed firmly to the rod (11), is mounted on the wall (22) so as topermit an axial movement of the rod during the operative travel of theclosure member (5 b) for the opening/closure of the seat (5 a).
 5. Adevice according to Claim 1, wherein the facing sides of the closuremember (5 b) and of the second diaphragm (24), respectively, aresubjected to the delivery pressure of the gas through the device.
 6. Adevice according to claim 4, wherein the rod (11) for operating theclosure member (5 b) extends through the second diaphragm (24).
 7. Adevice according to claim 1, wherein the biasing member comprises aspring (7) acting directly on the closure member (5 b) in order to urgeit towards the shut-off position.
 8. A device according to claim 1,wherein the portion of the duct (9) of the control circuit that extendsbetween the solenoid valve (8) and the control chamber (10) is connectedto a pilot duct (14) for the supply of gas to a respective pilot burner.9. A device according to claim 1, wherein the first side (6 a) of thediaphragm (6) delimiting the control chamber (10) is subjected to thegas-supply pressure gas through the main duct (2).
 10. A deviceaccording to claim 1, further comprising a delivery-pressure regulatormember (20) in the duct (2), downstream of the valve seat (5 a).
 11. Adevice according to claim 10 wherein the regulator member (20) comprisesa second diaphragm servo-valve (25) arranged in series with thediaphragm valve (5) with respect to the direction of the gas-flow, thesecond servo-valve (25) including a diaphragm pressure regulator (30).12. A device according to claim 11 in which the second servo-valve (25)comprises a respective second control solenoid valve (29) with anelectromagnetic operator for controlling the opening/closure of thesecond servo-valve (25), the second solenoid-valve being arranged to actso as to open/close a duct (28) of a respective servo-assisted controlcircuit (28, 32) so as to operate the closure member (25 b) of theservo-valve (25) indirectly by the diaphragm control.
 13. A deviceaccording to claim 12, wherein both of the ducts (9, 28) for tapping offthe control pressures of the respective control circuits, which ductscan tap off a pressure signal for transfer to the corresponding controlchambers (10, 32), are connected to and in flow communication with themain duct (2) upstream of the first valve (5).
 14. A device according toclaim 12, wherein a control-pressure tapping duct (28), of thecorresponding control circuit, which duct can tap off the pressuresignal for transfer to the respective control chamber (32), is connectedto and in flow communication with a portion of the main duct that isdisposed between the valve seats (5 a, 25 a) of the respective valves(5, 25).
 15. A device according to claim 11, wherein the diaphragmpressure regulator (30) is disposed in a portion (35) of duct of thecontrol circuit of the second servo-valve (25) which extends between thecorresponding control chamber (32) of the second servo-valve (25) and aportion of the main duct (2) downstream of the second servo-valve (25).